Animal and vegetable rendering presses and the like include a variety of working parts such as screw flights, breaker bars and pins and metallic screens that are subjected to excessive shear conditions during the kneading and working of the abrasive animal or vegetable medium in the press. In animal rendering operations, the work medium is acidic, and accordingly, the working parts must be capable of enduring in this corrosive environment in addition to fulfilling the requirement of good wear resistance.
In many cases, carbon steel, Ni, Cr and B alloys have been used to make such press parts but, in the long run, these parts exhibit an undesirable brittleness or excessive corrosion that may lead to fracture.
Ni.backslash.Cu Monel alloys with minor amounts of Si addition thereto are known as being corrosion resistant in many acidic mediums. However, brittle suicides may be present in these alloys and this leads not only to difficulty in machining of the desired parts but also to the possible fracture failure of the part during prolonged use.
There is accordingly a need in the art for the provision of fracture tough, ductile metallic parts that exhibit high impact strengths so that such parts can be used as working parts in the expression, kneading or shearing of abrasive materials. There is an even more specific need for the provision of such parts that are corrosion resistant in acidic media.